This invention relates to the stabilization of organic material normally tending to deteriorate. In particular, the invention relates to the protection of synthetic polymers against the harmful degradative effects, such as discoloration and embrittlement caused by exposure to light, especially ultraviolet light.
It is known that actinic radiation, particularly in the near ultraviolet region, has a deleterious effect on both the appearance and properties of organic polymers. For example, normally colorless or light colored polyesters yellow on exposure to sunlight as do such cellulosics as cellulose acetate. Polystyrene discolors and cracks, with accompanying loss of its desirable physical properties when exposed to actinic light, while vinyl resins, such as polyvinyl chloride and polyvinyl acetate spot and degrade. The rate of air oxidation of polyolefins such as polyethylene and polypropylene is materially accelerated by ultraviolet light.
It is also known to use certain metal salts of aminoacids for the stabilization of polyolefins against degradation by heat and light and as dyesites. For example, in U.S. Pat. No. 3,102,107, nickel salts of .alpha.-aminocarboxylic acids are disclosed as stabilizers of polyolefins against degradation by light. In Japanese Pat. Nos. 4275/67, 3183/67, and 3179/67, there are disclosed certain metal salts of N-alkyl-.beta.-aminopropionates as additives for dyeable polyolefin compositions. We have now found that if, instead of the above metal salts of amino acids, certain metal salts of N,N-disubstituted .beta.-alanines are used as stabilizers for organic materials against degradation by light, a significant and unexpected enhancement in light stabilizing activity results.